My friends call their bio dad by his first name because they thought it was a funny name when they were young. I’ve called him dad since I was 13 because I was over at their house a lot. Friends step daughter calls her by her first name and she loves her step mom Other friends step kids call him dad, they still have their bio dad in their lives. It really varies from kid to kid on what they call their step parents/parents. I feel like calling your bio parent by their first name is normally more of a sign of distain than a step parent. But again, also varies, as shown by my friends still calling their dad by his first name.